Many processes are known for making prototypes of engineered components. Woodworking techniques have long been used, and find continued use in many industries. Metalworking techniques have also been used; metal prototypes are machined from solid forgings and castings, and they are also fabricated from sheet metal. Obviously, woodworking and metalworking techniques require significant levels of skill, as well as a significant amount of manipulation by the human hand. They also require detailed engineering drawings of the prototype which define its geometry and dimensions. After the prototype is made, it is inspected to verify whether or not it conforms to the drawing; if it doesn't, the prototype is remade. And even if the prototype conforms to the drawing, the designer or engineer may wish to modify a feature of the prototype, which requires a modification of the drawing and repetition of the prototype fabrication and inspection process.
Presently, there is a significant effort being put into the development of processes for making prototypes directly from computer aided design (CAD) files. See, for example, U.S. Pat. Nos. 4,929,402 4,575,330 to Hull, and 4,863,538 to Deckard, and 4,752,498 to Fudim. According to the processes described in these patents, prototypes are formed using apparatus which interprets a CAD file of a part and then guides an energy beam, such as a laser, onto a medium capable of solidification when impinged upon by the beam. The prototype part is built up layer by layer, by forming and joining together adjacent cross sectional layers to each other.
Processes of the type described above are referred to as rapid prototyping processes; they are particularly adapted for making prototype parts having internal and external surfaces, such as parts having a hollow internal cavity. Each cross section, or layer, for such types of parts is defined by closed curves; an inner closed curve represents the internal surface of the part and an outer closed curve represents the external surface of the part. The distance between the curves corresponds to the part thickness at that cross sectional layer.
Much progress has been made in the effort to reduce the amount of time and money required to produce prototype parts. However, the prototypes produced using the CAD based processes in the above mentioned patents typically have a polymeric composition. Testing or use of such parts in high temperature or high stress environments cannot readily be performed for obvious reasons. Metal prototypes can be tested in such environments, but the prior art does not describe processes for making such parts rapidly and cost effectively. Accordingly, what is needed is a rapid and cost effective process for making metal prototype parts. This invention satisfies such needs.